The invention relates to a method for constructing and operating a leaf bascule bridge that uses a cable system for driving the leaf bascule bridge.
Leaf bascule bridges are well known to the civil engineering professionals and their advantages are recognized by those skilled in this art.
Known methods for operating leaf bascule bridges are, either a mechanical system, or a hydraulic system; in which both methods the moving leaf rotates about a fixed axis on trunnions attached to the bascule bridge structure, and a weight at the end of the bascule structure is provided to counterbalance the weight of the cantilevered structure.
To drive the bascule bridge, a pushing force is applied to the front of the trunnions by a mechanical system mounted to the inside of the bascule pier.
The shortcomings of the existing methods are:
the driving system, either mechanical or hydraulic, is very complicated and requires qualified operators and continuous maintenance,
the arm of the force applied to the leaf bascule bridge is small, requiring a large pushing force for driving the bascule bridge,
the length of the bascule pier is required to be large in order to accommodate the driving mechanisms,
the time required for operating a lifting cycle is lenghty, reducing the traffic capacity of the roadway.
To overcome the shortcomings of the existing methods, this invention is developed to produce a leaf bascule bridge operated by a cable system with a simplified and more efficient driving system. It utilizes a narrow bascule pier a longer span and uses a pulling force with a large arm applied to the end of the counterweight, in back of the trunnion, instead of a pushing force with a small arm applied to the front of trunnion.